Gareth Lee, a volunteer member of the LGBT advocacy group Queer Space, claimed he was left feeling like a lesser person when his order, which had been paid in full, was turned down.

Ashers, run by the McArthur family, declined the request for a cake with an image of Sesame Street puppets Bert and Ernie below the motto Support Gay Marriage.

It had been ordered for a private function marking International Day Against Homophobia last May.

District judge Isobel Brownlie heard that nine members of the McArthur family work in the business which delivers across the UK and Ireland.

Mrs McArthur and her husband Colin, who belong to Dunseverick Baptist Church, are the only two shareholders with voting rights on how the company is run.

Their three sons are members of different Protestant churches.

Under cross-examination from Robin Allen QC who is representing Mr Lee, Mrs McArthur told the court she had been a born-again Christian since the age of seven and sought to please God in how she led her life.

She took the order from Mr Lee in order to avoid a confrontation in the bakery, she claimed.

“I did not want to embarrass him or have a confrontation in the bakery,” Mrs McArthur told the court.

Public opinion on the landmark civil case has been split in Northern Ireland and beyond.

The Equality Commission had initially asked for the bakery on Belfast’s Royal Avenue to acknowledge it had breached legislation and offer ‘modest’ damages to the customer.

When Ashers refused, the commission, a publicly funded watchdog, proceeded with the legal action.

Daniel McArthur, general manager of Ashers has accused the commission of pursuing his family because of their belief marriage should be between man and woman.

Speaking ahead of the case, which began yesterday, Mr McArthur said he had been humbled by the level of support from Christians worldwide and was putting his faith in God.

Ashers Bakery, which employs around 80 people, has been backed by the Christian Institute lobby group, which has arranged public meetings and garnered financial backing for the legal action.

Same-sex marriage remains a contentious issue in Northern Ireland and attempts to have it legalised have been repeatedly rejected by the devolved Assembly at Stormont.

The cake row has prompted a proposal to include a so-called conscience clause' in equality legislation.

The Democratic Unionist Party, whose MLA Paul Givan is bringing forward the Private Members' Bill, says businesses should have the right to refuse to provide services they believe could compromise their religious beliefs. However, Sinn Fein has vowed to veto the move.